SPM: Partial implementation of PSA interrupt control APIs

This patch implements two of the Secure Partition APIs for
interrupt control defined by FF-M v1.1:
 - psa_irq_enable
 - psa_irq_disable
Implement only these two for SLIH for the time being.

Change-Id: Ia1103b2d70f1406e2ad0100d856f9e11568c2430
Signed-off-by: Kevin Peng <kevin.peng@arm.com>
6 files changed